Apparatus for continuous steel refining



Sept. 2, 1969 cHuNG-wls cHANG 3,464,687

APPARATUS FOR CONTINUOUS STEEL REFINING 2 Sheets-Sheet 1 Filed DeC. 1,1966 Fig./

Chung-Wie Chang INVENTUR.

Sept. 2, 1969 cHUNGwIE cHANG 3,464,687

APPARATUS FOR CONTINUOUS STEEL REFINING 2 Sheets-Sheet 2 Filed Dec. l,1966 Fig. 2

Chung- Wi@ Chang INVISNTOR,

United States- 3,464,637 APPARATUS FOR CGNTINUOUS STEEL REFININGChung-Wie Chang, 10 1st Chian Sen St., Kaohsiung, Taiwan Filed Dec. 1,1966, ser. No. 593,403 Int. Cl. CZlc /48; F2711 3/10 U.S. Cl. 266-37 6Claims ABSTRACT OF THE DISCLOSURE The present invention generallyappertains to furnaces and processes for making steel and moreparticularly relates to a novel method and furnace for effectingcontinuous steel refining from the molten unpurifled iron state to thefinal refined steel state.

In the usual process of making steel, iron ore compounds are subjectedto a smelting procedure so as to reduce the ore to a molten state, knownas molten pig iron. The reduction of iron ore to pig iron is carried outin conventional blast furnaces and then the refining step is carried outwherein the molten unpurified iron from the smelting furnace issubjected in batches to the action of oxygen and of ux ingredients forrefining the molten charge. Such treatment is known as batch treatmentwhich is effected by a conventional batch converter. Such batchconverter requires an iron mixer and heavy cranes for charging anddischarging purposes, for moving and rotating equipment and largefoundations. In such batch treatment, oxygen is introduced into theconverter, which is a Vessel containing a molten charge, the chargebatch being subjected to the action of the oxygen for a periodsufiicient to refine the entire contents of the converter. Then, thetreated molten batch is poured into other equipment, such as ladles, forfurther processing.

Conventional batch processing, using conventional batch converters andattendant cranes and other moving and rotating equipment, necessitatestime delays due to the emptying and refilling of the converter for eachcharge to be refined and necessitates considerable equipment, whichincreases the cost of processing steel on a large scale and has thedrawback that the refined steel varies from batch to batch so that thereis a lack of uniformity.

An important object of the present invention is to provide a process andapparatus for effecting a continuous refining of the steel so that thereis no refilling and emptying cycle as required by the conventional batchconverter.

Another important object of the present invention is to provide aprocess and apparatus for carrying out the continuous refining of steelfrom the constant'introduction of molten iron at one point into thehearth of a heated furnace and the constant withdrawal of the refinedsteel from another point in the furnace, which process and apparatus canbe used in conjunction with conventional blast furnaces and continuouscast molding equipment.

Another important object of the present invention is to provide a methodof continuously refining molten unpurified iron by introducing themolten iron at one point into the hearth of a heated furnace and passingthe molten iron in a continuous but separated zigzag inclined coursearent 0 3,454,687 Patented Sept. 2, 1969 from the inlet to an outletwith the separated channels of the course being progressively greater involume and being inclined in reverse fashion from the inlet to theoutlet, subjecting the molten iron in its passage along the courses tooxygen in a very `simple but highly effective manner and adding, atvarious points, along the course additional scraps and drawing off slagat certain points along the course.

Another object of the present invention is to provide, in combinationwith the foregoing object, the additional steps of adding scraps to thecontinuously moving molten iron so that as the molten iron and scrapstravel further through the zigzag course, defined by channels in thehearth of a continuous steel furnace, constructed in accordance with thepresent invention, the silicon content of the charge will be eliminatedto 0'.0l5-0.20% and, at such stage, the slag can be removed. In themeantime, the oxidation rate of manganese and carbon is increased tocomplete the refining process.

Another important object of the present invention is to provide, in theforegoing process, the step of adding alloy metals to the constantly andcontinuously moving molten steel, as the carbon content is decreased tothe required point.

Another important object of the present invention is to provide a novelcontinuous steel refining furnace having a hearth formed with endcommunicating separated channels arranged in a zigzag course, from aninlet to an outlet, with the channels being formed in reverse inclinedfashion and in progressive wider sizes so that the molten iron will flowspeedily in the zigzag course and so that volume of the molten iron canbe increased from channel to channel by adding scraps or alloy metalscan be added to the channels, such means being associated with the sidesof the furnace and including novel structural means at the ends of thechannels whereby slag may be drawn off and whereby scraps or alloymetals may be added without disturbing the continuous and constant flowof the molten iron.

Another important object of the present invention is to provide a noveloxygen lance arrangement in association with the channels whereby therate of oxygen can be controlled and whereby the oxygen from the lancenozzles is uniformly distributed, thus making it possible to controlmore easly the quality of the steel. Further, in connection with suchobject, the air pressure is not as high as that used in the batchconverter which is equipped with large lances and, thus, erosion of theair to the refractory is reduced.

Another important object of the present invention is to provide acontinuous operation, which is much safer than a batch process and whichis considerably reduced, from an economic and time standpoint, incomparison with conventional batch converters or other known apparatusfor a continuous process of steel making.

Another important object of the present invention is to provide aprocess and apparatus for the continuous refining of steel whereby thequality of the steel products is much better than that from batchprocesses or other processes or apparatuses for continuous steel making.

These together with other objects and advantages which will becomesubsequently apparent reside in the details of construction andoperation as more fully hereinafter described and claimed, reference=being had to the accompanying drawings forming a part hereof, whereinlike numerals refer to like parts throughout, and in which:

FIGURE 1 is a horizontal, cross-sectional View of a furnace, constructedin accordance with the present invention;

FIGURE 2 is a vertical, longitudinal sectional view, taken substantiallyon line 2 2 of FIGURE 1 and showing the arrangement of the channels inthe hearth of the furnace and illustrating the means for withdrawingslag and for adding scraps or alloy metals;

FIGURE 3 is a vertical, cross-sectional view, taken substantially online 3 3 of FIGURE 1 and showing in section the furnace construction andin elevation one of the oxygen lances, illustrating the arrangement ofthe oxygen lance and its orientation with respect to one of thechannels, it being understood that an oxygen lance will overlie each ofthe channels and be in operative association therewith, as shown inFIGURE 3;

FIGURE 4 is a fragmentary, detailed vertical, crosssectional view, takensubstantially on line 4 4 of FIG- URE 1 and illustrating means wherebyadditional charges, such as scraps or alloy metals can be added to thecontinuous zigzag course in the hearth, which course is made up of thechannels, which are individual and separate but are in communication attheir ends to form the zigzag course from the inlet to the outlet;

FIGURE 5 is a fragmentary longitudinal vertical sectional view, takensubstantially on line 5--5 of FIGURE l and showing the means wherebyslag may be withdrawn at certain of the ends of the intercommunicatingchannels and the ends may be charged with iron scraps; and,

FIGURE 6 is a fragmentary cross-sectional view, taken substantially online 6-6 of FIGURE 3 and illustrating in detail the construction of theoxygen lances.

Referring now more particularly to the accompanying drawings, thereference numeral 10 generally designates a steel refining furnace,which is constructed in accordance with the present invention and whichincludes a hearth 14 from which end walls 16 and 18 upstand. AS shown inFIGURE 3, the furnace further includes upstanding side walls and 22which have inwardly inclined upper end portions 24 and 26 providing anupper open end 28. The furnace is formed from suitable conventionalmaterials, such as brick or other refractory materials.

The hearth 14 is formed with a continuous zigzag, communicating course,constituted by zigzaggedly arranged, intercommunicating channels 30formed in the upper surface of the hearth 14. The channels are formed ina continuous zigzag pattern from the end wall 16 to the end wall 18 withthe channel 30a constituting an inlet channel in communication with theinlet 32 and the channel 30h constituting an outlet channel incommunication at its outer end with an outlet 34. The molten unpurifiediron from the smelting furnace is introduced constantly and continuouslyinto the inlet 32 and flows constantly and continuously through thecourse, defined by the zigzag, intercommunicating series of channels 30to and through the outlet 34 from which it emerges as molten renedsteel.

As the molten iron passes through the channels, an oxygen or oxygen-richgaseous stream, in the form of jet blasts, is directed onto the moltenmetal in each course. Thus, an oxygen lance 36 is provided inassociation with each of the channels. For the sake of simplicity, onlyone lance has been shown and has been shown in structural and functionalassociation with the channel 30a.

The oxygen lance 36 comprises an annular outer re brick wall 38, whichextends through openings 39 in the side walls 20 and 22 and ispositioned above the channel 30a and is disposed parallel therewith andextends the full length thereof. Concentrically arranged within theouter re brick annular wall 38 is an annular water pipe 40 through whichWater passes. The pipe 40 is formed, exteriorly of the furnace, with aninlet 42, at one end thereof, and an outlet 44 at the other end thereof.Concentrically arranged within the water pipe 40, through which waterpasses from the inlet 42 to the outlet 44 is an annular inner pipe 46,which carries oxygen. The pipe 46 is formed with radially projectingnozzles 48 that pass through the hollow interior of the water pipe 40and through radial openings 50 in the outer fire brick covering 38 andhave outlet jet ends 52 from which oxygen jet blasts S4 project, theblasts 54 projecting downwardly onto the molten iron in the channel 30a.In this respect, it is to be noted that the oxygen lance 36 is spacedvery slightly above the upper surface of the Walls defining the channel30a so that the blasts 54, which are spaced veryv close together andevenly along the entire length of the lance 36 are directed onto theentire moving portion of the molten iron passing through the channel30a. This is also true of the lances provided in structural andfunctional association with each of the other channels 30 in the seriesfrom the end wall 16 to the end wall 18.

It can thus be seen that the oxygen blasts 54 from the lance nozzles 36are uniformly distributed. This makes it possible to control more easilythe steel quality. The air pressure is not as high as that used in abatch converter or in known furnaces which are equipped with largelances or which have lances with the oxygen projecting forcibly from endnozzles. There-fore, erosion of the air to the refractory is reduced.

The molten pig iron, as aforestated, is introduced into the initialchannel 30a through the inlet 32, in the side wall 2i) adjacent the endwall 16. The channels 30 slope back and forth from the side Wall 20 tothe side wall 22, as can be appreciated from FIGURES 2 and 3. Thus, eachadjoining channel is inclined in an opposite direction between the sidewalls 20 and 22 from the initial inlet channel 30 or to the inal outletchannel 30h. An outlet 34 is formed in the side wall 20 adjacent the endWall 18 and in outlet communication with the outlet channel 3017. It canbe appreciated, from a consideration of FIGURE 2, that the channels 30are formed in progressive wider sizes lbut are of the same depth so thatthe volumetric capacity of the channels is progressively increased byvirtue of the progressive increase in the width of the successivechannels from the inlet end wall 16 to the outlet end wall 18. In otherwords, the channels progress in wider sizes and even fashion so that theinlet channel 30a is smaller in width than the outlet channel 30h, ascan be appreciated from a consideration of FIGURE 2. The reason for thisis that the volume of the molten iron will be increased from channel tochannel by adding scraps or alloy metals in the refining stages, while,due to the reverse inclination or slope of the channels, the molten ironwill flow at a fast constant rate through the zigzag course from theinlet 32 to and through the outlet 34.

The channels are divided or formed by partition Walls 56, which extendfrom the side wall 20 and terminate in concave free ends 58 that arespaced from the side wall 20, and by parallel partition walls `60 whichextend from the side wall 20 and terminate in free concave ends 62 whichare spaced from the side Wall 22. It is by virtue of the partition wallsthat the channels are formed and by virtue of the arrangement of thepartition walls, some projecting from the side Wall 22 and being spacedfrom the side wall 20 and some extending from the side wall 20 and beingspaced from the side wall 22 that the individual channels are formed ina zigzag 'but communieating fashion. In other words, the channelscommunicate at their opposing ends.

In the latter respect, arcuate communicating spaces 64 are formedbetween the channels, adjacent the side wall 20, shown in FIGURES 1 and2. The communicating spaces 64 are on the interior of the side wall 20and are ofthe same depth as the channels.

The purpose for the communicating spaces 64, which are realized by theterminating ends 58 of the partitions 56 that project from directstructural relation with the inner surface of the side wall 22, is toprovide intercommunicating means and to provide arcuate communicatingpockets for the reception of additional charges 66 of scraps or alloymetals, the scraps or alloy metals 66, as shown in FIGURE 4, beingintroduced into the communicating pockets or portions 64 through chargedoors 68 formed in the side wall 20, as shown in FIGURES 1 and4.

By virtue of the termination of the ends 62 of the f partitions 60 at adistance from the inner surface of the side wall 22, pools 70 areestablished. The pools 70, as shown in FIGURE 5, are arcuate or curvedin crosssection and are concave in vertical dimension and are of a depthgreater than the depth of the channels, as can be appreciated from aconsideration of FIGURES 3 and 5.

The purpose of forming the pools so that they are arcuate and are of agreater depth in communicating the channels at their ends adjoining theside wall 22 is to provide draw off doors 72 formed inthe side wall 22adjacent the upper most portion of the lower end of the channel slantedor inclined toward the side wall 22, as can be appreciated from FIGURE5. The slag discharge doors 72 permit the slag to be skimmed off theconstantly ilowing Imolten iron and to assist, in this regard, baffleplates 74 are vertically formed between the side wall 22 and the ends 62of the partitions 60 with the baille plates 74 -being disposed in aplane at the upper ends of the pools 70 and having upper edges 76 whichlie coplanar with the upper edges of the partition walls, while havinglower edges 7 S which are spaced considerably above the bottom walls ofthe pools 70, as shown in FIGURE 5. Thus, the ilowing molten material,which ilows more rapidly toward the side wall 22, is forced to flowunder the baille plates 74 and around the lower edges 78 thereof andthis permits the slag to be drawn off through the sla-g discharge doors72.

Charge doors 82 are formed in the side wall 22 above the pools 70 andare arranged on the downstream side of the partition 74, that is, on theside of the partitions facing the end wall 18 and are provided and soarranged so that scraps or alloy metals can be added to prevent damagefrom charging scraps into the pool 70.

The operation of the furnace is extremely simple. Before charging themolten pig iron, the furnace 10 is preheated to about 2500-2800 F., withan conventional method. Then, molten pig iron and lime, if used, ischarged into the furnace from the inlet 32. The ilow is constant andcontinuous and, as the molten pig iron passes through the zigzag coursefrom the inlet 32 to the outlet 34, the course -bein-g defined by thereversely downwardly sloped or inclined endwise intercommunicatingchannels 30 in series, oxygen is delivered from the lances 36. The rateof oxygen is controlled to approximately 20 pounds per hour for eachnozzle. Scraps `66, if added, are charged into the spaces 64 or arecharged into the pools 70 through the charge doors 68 and 82.

Oxidation of silicon and manganese in the charge will be noted at theilrst stage in the reiining process. Heat evolution from this proces isutilized for melting the solid scraps 66 which are added. The limecombines with silicon formed by selective oxidation of silicon and formsa liquid slag. In the iirst stage of steel refining as the materialpasses through the initial part of the zigzag course there is verylittle oxidation of carbon.

As the molten iron and scraps ilow further through the channels and therefining process continues, the silicon content of the charge will beeliminated to 0.0l5-0.20%. It is at this stage that the slag, as formedin the iirst Stage, can be removed, through the slag discharge orremoval doors 72. In the meantime, the oxidation rate of carbon isincreased to complete the reiining process. As the carbon content isdecreased to the required point, alloy metals may be added through thecharge doors 68 or 82 as required by the process to make alloy steel.

As pointed out in the foregoing, the reason why the channels 30 areformed in progressive wider sizes is that the volume of the molten ironwill be increased from channel to channel because of the addition ofscraps or alloy metals in the reiining Stages.

As noted in FIGURE 5, molten iron and slag will ilow toward the pools 70and the baille plate 74 will cause the aletas? ilo-w to flow thereunderand will permit the slap to be discharged through the slag dischargedoors 72.

As required by the reiining process, addition of ilux such as lime,silica, and the like can be made at the pools 70 while the alloymaterials 66 can be charged at the portions 64. However, this is merelya desired practice and it can be appreciated that the charge doors 68and 82 can be used for adding alloy, scraps or steel alloys, as theprocess continues, while lime, silicates and the like can be added tothe constantly flowing molten iron, during the continuous process,through the charge doors 82.

It can be appreciated that the furnace provides a continuous steelreiining process and that there is norefilling and emptying cycle, asrequired by the conventional batch converter. Further, the furnacecapacity can be increased as the operation continues, due to the arrangement and construction of the channels and the provision of the chargedoors in the side walls and the provision and arrangement of thechannels and communication of the ends thereof at the spaces 64 andpools 70'.

It can also be appreciated that there is no thermal shock to the furnacerefractory due to the fact that the temperature'is constant and uniformin the continuous operation as the molten iron ilows continuously andconstantly from the inlet 32 to the outlet 34 and is treated by theoxygen blasts 54 from the oxygen lances 36 that is the addition of fluxsuch as lime, silicates and the like, as required by the refiningprocess.

The life of the furnace refractory is considerably increased becausethere are no impact forces upon the refractory and the hearth isconstructed, by virtue of the formation of the zigzag courses orchannels, so that there is an even distribution of heat and constant andcontinuous ow of molten iron.

The oxygen from the lance nozzles 36 is uniformly distributed and thismakes it possible to control the steel quality more easily. The airpressure is not as high as that used in a batch converter which isequipped with large lances, as aforestated, so that erosion of the airto the refractory is reduced.

Furthermore, it can be appreciated that the continuous operation, asafore briefly described and which can be appreciated from aconsideration of the drawings, is much safer than a batch process. Itcan also be appreciated that only a small foundation is needed for thestationary furnace and that no moving parts or components are requiredand that no heavy cranes lare needed for charging and discharging sothat the furnace costs can be greatly reduced. It has been found thatthe continuous steel reiining operation, made possible by the processand furnace of the present invention, results in considerable reductionsin costs while the quality of the steel products from the furnace ismuch better.

If desired, the end spaces or communicating portions may be formedexactly as the pools 70 so that there would be pool and baillearrangements with slag draw-off or discharge doors at each of the sides20 and 22.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous modiiications and changes willreadily occur to those skilled in the art, it is not -desired to limitthe invention to the exact construction and operation shown anddescribed, and accordingly all suitable modifications and equivalentsmay be resorted to, falling within the scope of the invention asclaimed.

What is claimed as new is as follows:

1. A steel reiining furnace comprising a hearth enclosed by upstandingWalls, a plurality of substantially parallel channels `defining saidhearth with adjacent channels having one end communicating to deiine acontinuous flow path, means at one end of said path for admitting moltenunpurified iron, means at the other end of said path for dischargingmolten purified iron, said path being inclined along said ilow path fordischarging impurities from the molten iron, and means along said liowpath for discharging oxygen into contact with the molten iron.

2. The furnace as dened in claim 1 together with means along said flowpath for admitting scraps into the molten iron, said means dischargingoxygen including pipe means overlying said hearth and having a pluralityof downwardly discharging nozzles.

3. A continuous steel refining furnace comprising a hearth havingopposing ends and opposing sides, a series of separated channels formedin the -upper surface of the hearth and extending in substantiallyparallel and separated fashion from one side to the other parallel withthe ends, one of the channels at one end having an inlet for molten pigiron .and the channel at the other end having an outlet for puriiiedmolten steel, said channels being in communication at their ends at eachside, one of said sides being provided with means for the introductionof scraps into the communicating ends of adjoining channels and thepoint of communication of the channels at least at one side includingthe formation of pools in the hearth, said pools being of greater depththan the channels.

4. The invention of claim 3, wherein said adjoining channels are slopeddownwardly in opposite directions from one side to the other side.

S. The invention of claim 4 and including means at the pools permittingslag to be withdrawn from the channels and vertical baffle platesoverlying the pools and spaced from the bottoms thereof and coplanarwith the tops of the communicating channels.

6. .The invention of claim 5 and including oxygen lances extendingtransversely of the hearth and longitudinally overlying each of thechannels parallel therewith, said oxygen lances having jet nozzle meansspaced along their lengths whereby jet blasts of oxygen are evenlydistributed onto the molten iron passing through each channel.

References Cited UNITED STATES PATENTS 2,526,472 10/ 1950 Gilliland266-34 X 3,343,828 9/1967 DA Hunt 266-33 X 3,288,594 11/ 1966 Smith75-65 X J. SPENCER OVERHOLSER, Primary Examiner R. SPENCER ANNEAR,Assistant Examiner U.S. Cl. X.R. 266--34

